A vigorous angiogenic response is a prominent component of normal wound repair. Within healing wounds, angiogenesis proceeds until vessel density more than doubles compared to uninjured tissue;most of these new vessels subsequently undergo apoptosis and are removed. While the mechanisms that guide the pro- angiogenic phase of healing are well-understood, the factors that regulate vascular regression in wounds are not yet clear. This project proposes to examine the mechanisms of vascular regression in the wound using well-established in vivo models. The overarching goal of this research is to evaluate the important molecular and spatio-temporal factors that cause blood vessel pruning and blood flow stabilization, and thereby contribute to successful wound resolution. The central hypothesis is that specific endogenous anti-angiogenic factors, including pigment epithelium-derived factor (PEDF) and vasostatin-I, drive vascular regression, allowing the resolving wound to come to vascular homeostasis. The primary aim of the current project is to discover the role of PEDF and vasostatin-I in the context of wound healing. The project will explore the mRNA and protein expression patterns of PEDF and vasostatin-I throughout the time course of healing in a well- characterized murine model of full-thickness dermal wounds. These proteins will be localized in the wound to evaluate the local cellular and structural environment with which they associate and interact. Comprehensive proof-of-function in vivo experiments will be performed to assess the role of endogenous PEDF and vasostatin- I in the resolving wound. These experiments will include the addition of supra-physiological levels of exogenous anti-angiogenic recombinant proteins to healing wounds. Also, interference with function of endogenous mediators will be performed via a novel method of delivery of small interfering RNA (si-RNA) nanoparticles and/or antibodies, followed by an assessment of their effect on wound vascularity using non- invasive laser Doppler imagining. The long term goal of this project is to develop a comprehensive understanding of the complex mechanisms that regulate wound angiogenesis. This knowledge will assist in the development of novel therapeutics to modify dysfunctional neovascularization and/or vascular regression in many human pathological conditions like cancer and arthritis, and will be especially applicable to the treatment of poorly healing wounds.